In the OP's original question, I don't see "diesel" mentioned. And her avatar shows a sailboat, so I assume we're talking about sailboat engines.

So ... I'll go out on a limb and tout the Atomic 4. Yes, I know there are issues here, especially with the idea of a gasoline engine in a sailboat. But the question was strictly about engines being "troublesome", and I don't think you can get much less troublesome than the old A4, especially with a couple upgrades like fresh watercooling, electronic ignition, electricfuel pump etc. And thanks to Moyer Marine, parts are available and reasonably priced, even entire new or rebuilt engines.

I think that a lot of engine issues are caused by a lack of use. Most boats sit for months and years without even starting the engine. This can lead to rings sticking or more likely some rust in the cylinders with an open intake valve.

Yanmar has had some dud's, but they make a heck of a lot of engines and are an OEM for some john deer engines. I was impressed when I found no measurable wear on the rings or bearings, crank after 1000 hours of use. I was less impressed that the piston lands broke, but then that is a know issue with earily 90's GM's

What annoys me the most is it is impossible to order parts online in California as no California dealer has a website for yanmar engine parts. Even the distributors website is un-usable. Yanmar has too restrictive dealer areas. Yes I can order a filter, alternator and maybe a water pump">raw water pump from go2marine or ebay.

So, generally, I have to go down to the city which takes well over an hour each way, and spend 1/2 hour or more talking to a dealer so they can cross check the part number and 9 times out of ten, order it from the distributor in costa masa, who has to order it from yanmars warehouse in Georgia. Then I pay two shipping charges, one from Georgia and one from SF to the boat. Lovely.

On the plus side other then engine mounts at $150 ish a piece, most of the yanmar internal engine parts are reasonably priced. At least they were not like Volvo.

My impression is it more model specific rather than brand specific. Volvo 2000 series aren't great, certain Yanmars aren't, I don't know of an older Perkins that has a common bad issue, but some of the newer relabeled ones do. There's a Diesel out there produced with a rubber timing belt.. forget who labeled it. Not a good engine sometimes. Some Volkswagen marine engines were terribly rough running, as were the BMW's.

I think Sailor Chic is right, low hours on an old engine is not necessarily good. A Perkins used in a commercialfishingboat, forklift, irrigation pump or continuously run gen set can go 20,000 hours no problem... Like a diesel in a semi truck that runs nearly continuously will go 500k miles. A diesel that is used to get in and out of the marina and never run that long may be shot at 1500 hours.

__________________"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard

FWIW, I understand Yanmar biggest market is in small diesel engines for rice harvesters, water pumps and other rice farming machinery. Their marine engines while prolific, are not their biggest market.

Not sure if that makes them better or worse but they have a lot of manufacturing experience in small(ish) diesels.

__________________All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence

My personal experience is with Yanmar, Westerbeke, and Universal. I've found the Universal (a Kubota block) the best and most reliable of the three. I had all three since new so I didn't inherit someone else's problems. The parts for the Universal are very reasonable if you buy from the transportation industry parts suppliers. My block is heavily used for reefer units in the transportation industry so parts are a fraction of what the marine dealers charge.

My boat has a Volvo 2003 motor, just shy of 30 years old, that runs great. A little oil smoke under heavy load. Only parts so far (had the boat 4 years) have been filters and raw water impellers. Maybe I'm just lucky?

Roger that. No green engines, especially ones with computers and no sail-drives. Yanmar runs full page ads now "All Mechanical, No computers". Sail-drives should be restricted to racing boats, preferably ones that haul out after every race. Hit something with a conventional shaft you may bend the shaft and ding the prop, hit something with a sale-drive or that forward-facing green motor thing and you may rip the whole bottom out of your boat.

Never had any serious problems with my Volvo MD2020s or sail drives in 14 years, but if starting from scratch I would have neither. Volvo's parts pricing (for parts they are just rebranding) is obscene (in fairness they are not alone). Saildrives are generally reliable, but crazy expensive for major repairs/replacement.

Have not owned a Beta, but sure like what I've read and heard. Well desinged for maintenance too...the Volvo MDs (actually Perkins) clearly did not have a maintenanceengineer on the design team...some things are a serious, and unecessary, PITA.

If I were to custom build my idea of the ultimate cruising cat then it would have Betas mounted midship and shafts (repairable anywhere in the world at reasonable cost with basic machine shop services).

I like the previous posters comment about not liking green engines. After owning several boats with different diesels and working on many more, I have learned all have their strong and weak points. But when it comes to volvo it is hard to find strong points.
They are plagued with oil and fuelleaks caused from poor design and you will be shocked at what you have to pay for repair parts. If you ask people who have repowered their boats that previously had volvo I doubt if you would find many that stayed with the brand

Even the old reliable Perkins engines leak oil like crazy, and have starters by the Price of Darkness. I thought Izuzu was a good engine until I talked to the fellow whose engine was ruined when the timing belt broke. Yanmar makes a lot of engines, but have more than their share of major failures, and some of their lines are difficult to work on. I've heard of Mercedes with broken valve springs. The Bene 423 group is overrun with reports of early failure of the Volvo flexible coupling. I'm partial to the Kubota based engines. but you still pays your money and takes your chances.

OTOH, for boat engine reliability all these diesels are miles ahead of the gasoline engines...

Well I dunno Julirmac
Everyone assumed you were talking about inboards and probably diesel
What about petrol outborda.
I was very disappointed to pay out for a new Honda 20HP long shaft 4 stroke to replace one of our two seven year old Hondas with blown piston after 1400hrs on our catamaran. It was serviced regularly by a Honda dealer and have generally been disappointed with their upkeep cost.
Could it be that Honda is resting on its laurels and other manufacturers have caught up with them for 50 to 70% of the price. Like Tohatsu perhaps
Granted it is the first 4 stroke marine engine I have had to contend with after earlier experience with similar sized Evinrude two strokes 30 years ago in tropical PNG that never saw a service and went on and on.